Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

Richard D. Andrews


The heartworm, Dirofilaria immitis, is widespread in dogs in North America and has been reported in wild canids in many states. This is a report of this parasite in hearts removed from coyote, red fox and gray fox carcasses collected in Illinois. A total of 415 coyotes had a significantly higher infection rate (23.6%) than 225 red foxes (3.6%) and 99 gray foxes (3.0%). Infection rates in red foxes and coyotes were significantly higher in or near the Wabash Border Natural Division along the eastern side of the state, suggesting a relationship between infection rates and this region. The mean number of worms in coyotes (8.1), red foxes (6.8) and gray foxes (1.3) did not differ significantly. Coyotes supported a maximum of 52 worms; red foxes, 21 worms; and gray foxes, 2 worms. An exponential decrease in the number of infected coyotes was noted as worm loads increased; 56.5% of 85 infections consisted of one to four worms, while only 16.5% of the infections had 15 or more worms. The percentage of the coyote sample with the potential to provide microfilariae to vectors (13.1%), based on the presence of both male and female worms, was significantly greater than the same parameter for both red foxes (1.3%) and gray foxes (1.0%).